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Membrane Bioreactor를 이용한 폭발성 물질의 가수분해 부산물의 탈질과정에의 적용
조경덕 ( Kyung Duk Zoh ) 한국물환경학회 2002 한국물환경학회지 Vol.18 No.2
A bench-scale anoxic membrane bioreactor (MBR) system, consisting of a bioreactor coupled to a ceramic crossflow ultrafiltration module, was evaluated to treat a synthetic wastewater containing alkaline hydrolysis byproducts (hydrolysates) of RDX, The wastewater was formulated the same as RDX hydrolysates, and consisted of acetate, formate, formaldehyde as carbon sources and nitrite, nitrate as electron accepters. The MBR system removed 80 to 90% of these carbon sources, and approximately 90% of the stoichiometric amount of nitrate, 60% of nitrite. The reactor was also operated over a range of transmembrane pressures, temperatures, suspended solids concentration, and organic loading rate in order to maximize treatment efficiency and permeate flux. Increasing transmembrane pressure and temperature did not improve membrane flux significantly. Increasing biomass concentration in the bioreactor decreased the permeate flux significantly. The maximum volumetric organic loading rate was 0.72 kg COD/㎥/day, and the maximum F/M ratio was 0.50 kg N/kg MLSS/day and 1.82 kg COD/kg MLSS/day. Membrane permeate was clear and essentially free of bacteria, as indicated by heterotrophic plate count. Permeate flux ranged between 0.15 and 2.0 ㎥/㎡/day and was maintained by routine backwashing every 3 to 4 day. Backwashing with 2% NaOCl solution every fourth or fifth backwashing cycle was able to restore membrane flux to its original value.
Occurrence and removals of micropollutants in water environment
Moon-Kyung Kim,Kyung-Duk Zoh 대한환경공학회 2016 Environmental Engineering Research Vol.21 No.4
Micropollutants are often discharged to surface waters through untreated wastewater from sewage treatment plants and wastewater treatment plants. The presence of micropollutants in surface waters is a serious concern because surface water is usually provided to water treatment plants (WTP) to produce drinking water. Many micropollutants can withstand conventional WTP systems and stay in tap water. In particular, pharmaceuticals and endocrine disruptors are examples of micropollutants that are detected at the drinking water, ppb, or even ppb level. A variety of techniques and processes, especially advanced oxidation processes, have been applied to remove micropollutants from water to control drinking water contamination. This paper reviews recent researches on the occurrence and removal of micropollutants in the aquatic environments and during water treatment processes.
Effects of molecular size fraction of DOM on photodegradation of aqueous methylmercury
Kim, Moon-Kyung,Won, A-Young,Zoh, Kyung-Duk Elsevier 2017 CHEMOSPHERE - Vol.174 No.-
<P><B>Abstract</B></P> <P>This study investigated the photodegradation kinetics of MeHg in the presence of various size fractions of dissolved organic matter (DOM) with MW < 3.5 kDa, 3.5 < MW < 10 kDa, and MW > 10 kDa. The DOM fraction with MW < 3.5 kDa was most effective in MeHg photodegradation. Increasing UV intensity resulted in the increase of photodegradation rate of the MeHg in all size of DOM fractions. Higher rates of MeHg degradation was observed at higher pH. For the portion of MW < 3.5 kDa, the photodegradation rate of MeHg increased with increasing DOM concentration, indicating that radicals such as singlet oxygen (<SUP>1</SUP>O<SUB>2</SUB>) radicals can be effectively produced by DOM. At higher portion of MW > 3.5 kDa, the inhibition of MeHg degradation was observed due to the effect of DOM photo-attenuation. Our result indicates that radical mediated reaction is the main mechanism of photodegradation of MeHg especially in the presence of MW < 3.5 kDa. Our results imply that the smaller molecular weight fraction (MW < 3.5 kDa) of DOM mainly increased the photodegradation rate of MeHg.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We examined the effect of DOM in humic substances on the photodegradation of MeHg. </LI> <LI> DOM fraction of MW < 3.5 kDa showed the highest photodegradation rate of MeHg. </LI> <LI> MeHg photodegradation increased at alkaline pH due to OH radical production. </LI> <LI> Photo-degradation of MeHg increased with increasing DOM concentration. </LI> <LI> Radicals produced by DOM under MW < 3.5 kDa increased photodegradation of MeHg. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Fate and Transport of Mercury in Environmental Media and Human Exposure
Kim, Moon-Kyung,Zoh, Kyung-Duk The Korean Society for Preventive Medicine 2012 Journal of Preventive Medicine and Public Health Vol.45 No.6
Mercury is emitted to the atmosphere from various natural and anthropogenic sources, and degrades with difficulty in the environment. Mercury exists as various species, mainly elemental ($Hg^0$) and divalent ($Hg^{2+}$) mercury depending on its oxidation states in air and water. Mercury emitted to the atmosphere can be deposited into aqueous environments by wet and dry depositions, and some can be re-emitted into the atmosphere. The deposited mercury species, mainly $Hg^{2+}$, can react with various organic compounds in water and sediment by biotic reactions mediated by sulfur-reducing bacteria, and abiotic reactions mediated by sunlight photolysis, resulting in conversion into organic mercury such as methylmercury (MeHg). MeHg can be bioaccumulated through the food web in the ecosystem, finally exposing humans who consume fish. For a better understanding of how humans are exposed to mercury in the environment, this review paper summarizes the mechanisms of emission, fate and transport, speciation chemistry, bioaccumulation, levels of contamination in environmental media, and finally exposure assessment of humans.
Kim, Moon-Kyung,Won, A-Young,Zoh, Kyung-Duk Informa UK (Taylor Francis) 2016 Desalination and water treatment Vol.57 No.2
<P>Photodegradation of methylmercury (MeHg) is an important process in mercury cycling that maintains low concentrations of MeHg in freshwater lakes; however, less is known about importance of this process in marine waters. The photo-induced formation of dissolved gaseous mercury (DGM, Hg-0) from MeHg removal was investigated. This study examined the effect of various environmental factors (i.e. light wavelength and intensity, and MeHg concentration), and primary water constituents on the abiotic photodegradation of MeHg, especially under different salinity. MeHg photodegradation rates were positively correlated with the UV light intensity, implying that the attenuation of UV radiation had a significant effect on MeHg photodegradation. However, a high dissolved organic matters concentration and salinity inhibited MeHg photodegradation. DGM was always produced during the photodegradation of MeHg. Photodegradation rates of MeHg and DGM production decreased with increasing salinity, suggesting that the presence of chloride ions inhibited MeHg photodegradation. Therefore, this study implies that MeHg in freshwater could be more rapidly demethylated than that in seawater. In other words, MeHg flowing into the lake or river would be almost removed by photo demethylation. However, MeHg flowing to seawater would be hardly removed, which could have more chance for bioaccumulation in seawater.</P>